1. Field of the Invention
The present invention relates to a monitoring apparatus, and more particularly, to a monitoring apparatus suitable for monitoring a digital video/audio signal.
2. Background Art
In recent years, video processing techniques have been improved, and thus a high-quality video broadcast, such as a high-definition television broadcast, has been provided. Here, digital video signals of a high-definition television broadcast, etc., are often transmitted to each home through satellite broadcasting and a cable TV network. However, an error sometimes occurs during the transmission of video signals from various causes. When an error occurs, problems, such as a video freeze, a blackout, noise, audio mute, etc., may result, and thus it becomes necessary to take countermeasures.
Under these circumstances, in Japanese Patent Application Laid-Open No. 2003-204562, the present applicant discloses, for example a signal monitoring system in which a central processing terminal calculates the difference between a first statistic value based on a video signal (first signal) output from a transmission source and a second statistic value based on a video signal (second signal) output from a relay station or a transmission destination, if the difference is below a threshold value, the transmission is determined to be normal, and if the difference is over the threshold value, a determination is made that a transmission trouble has occurred between the transmission source 10 and the relay station 20 so that a warning signal is output to raise an alarm (alarm display and alarm sound).
However, in the case of such a signal monitoring system, the central processing terminal only calculates the difference between the first statistic value and the second statistic value, and makes an automatic determination of a transmission trouble on the basis of the difference. Thus, there is a problem in that a sufficient analysis cannot be made on what kind of error has occurred from that determination. If a sufficient error analysis cannot be made, the same trouble may be brought about again. Here, in order to analyze an error, it is necessary to store all the transmitted video signals, and to check the signals while reproducing the signals later with taking time. However, in order to do that, it needs a vast amount of storage capacity for storing video/audio signals and enormous checking time.